Methods For Generating Melatonin-Response-Tuned White Light With High Color Rendering

ABSTRACT

The present disclosure provides methods for generating tunable white light with controllable circadian energy performance. The methods use a plurality of LED strings to generate light with color points that fall within blue, yellow/green, red, and cyan color ranges, with each LED string being driven with a separately controllable drive current in order to tune the generated light output. Different light emitting modes can be selected that utilize different combinations of the plurality of LED strings in order to tune the generated white light. One or more of the LED strings can have ultraviolet or violet LEDs.

FIELD OF THE DISCLOSURE

This disclosure is in the field of solid-state lighting. In particular,the disclosure relates to methods of providing white light with tunablecolor temperature and circadian energy performance.

BACKGROUND

A wide variety of light emitting devices are known in the art including,for example, incandescent light bulbs, fluorescent lights, andsemiconductor light emitting devices such as light emitting diodes(“LEDs”).

There are a variety of resources utilized to describe the light producedfrom a light emitting device, one commonly used resource is 1931 CIE(Commission Internationale de l'Éclairage) Chromaticity Diagram. The1931 CIE Chromaticity Diagram maps out the human color perception interms of two CIE parameters x and y. The spectral colors are distributedaround the edge of the outlined space, which includes all of the huesperceived by the human eye. The boundary line represents maximumsaturation for the spectral colors, and the interior portion representsless saturated colors including white light. The diagram also depictsthe Planckian locus, also referred to as the black body locus (BBL),with correlated color temperatures, which represents the chromaticitycoordinates (i.e., color points) that correspond to radiation from ablack-body at different temperatures. Illuminants that produce light onor near the BBL can thus be described in terms of their correlated colortemperatures (CCT). These illuminants yield pleasing “white light” tohuman observers, with general illumination typically utilizing CCTvalues between 1,800K and 10,000K.

Color rendering index (CRI) is described as an indication of thevibrancy of the color of light being produced by a light source. Inpractical terms, the CRI is a relative measure of the shift in surfacecolor of an object when lit by a particular lamp as compared to areference light source, typically either a black-body radiator or thedaylight spectrum. The higher the CRI value for a particular lightsource, the better that the light source renders the colors of variousobjects it is used to illuminate.

Color rendering performance may be characterized via standard metricsknown in the art. Fidelity Index (Rf) and the Gamut Index (Rg) can becalculated based on the color rendition of a light source for 99 colorevaluation samples (“CES”). The 99 CES provide uniform color spacecoverage, are intended to be spectral sensitivity neutral, and providecolor samples that correspond to a variety of real objects. Rf valuesrange from 0 to 100 and indicate the fidelity with which a light sourcerenders colors as compared with a reference illuminant. In practicalterms, the Rf is a relative measure of the shift in surface color of anobject when lit by a particular lamp as compared to a reference lightsource, typically either a black-body radiator or the daylight spectrum.The higher the Rf value for a particular light source, the better thatthe light source renders the colors of various objects it is used toilluminate. The Gamut Index Rg evaluates how well a light sourcesaturates or desaturates the 99 CES compared to the reference source.

LEDs have the potential to exhibit very high power efficiencies relativeto conventional incandescent or fluorescent lights. Most LEDs aresubstantially monochromatic light sources that appear to emit lighthaving a single color. Thus, the spectral power distribution of thelight emitted by most LEDs is tightly centered about a “peak”wavelength, which is the single wavelength where the spectral powerdistribution or “emission spectrum” of the LED reaches its maximum asdetected by a photo-detector. LEDs typically have a full-widthhalf-maximum wavelength range of about 10 nm to 30 nm, comparativelynarrow with respect to the broad range of visible light to the humaneye, which ranges from approximately from 380 nm to 800 nm.

In order to use LEDs to generate white light, LED lamps have beenprovided that include two or more LEDs that each emit a light of adifferent color. The different colors combine to produce a desiredintensity and/or color of white light. For example, by simultaneouslyenergizing red, green and blue LEDs, the resulting combined light mayappear white, or nearly white, depending on, for example, the relativeintensities, peak wavelengths and spectral power distributions of thesource red, green and blue LEDs. The aggregate emissions from red,green, and blue LEDs typically provide poor CRI for general illuminationapplications due to the gaps in the spectral power distribution inregions remote from the peak wavelengths of the LEDs.

White light may also be produced by utilizing one or more luminescentmaterials such as phosphors to convert some of the light emitted by oneor more LEDs to light of one or more other colors. The combination ofthe light emitted by the LEDs that is not converted by the luminescentmaterial(s) and the light of other colors that are emitted by theluminescent material(s) may produce a white or near-white light.

LED lamps have been provided that can emit white light with differentCCT values within a range. Such lamps utilize two or more LEDs, with orwithout luminescent materials, with respective drive currents that areincreased or decreased to increase or decrease the amount of lightemitted by each LED. By controllably altering the power to the variousLEDs in the lamp, the overall light emitted can be tuned to differentCCT values. The range of CCT values that can be provided with adequateCRI values and efficiency is limited by the selection of LEDs.

The spectral profiles of light emitted by white artificial lighting canimpact circadian physiology, alertness, and cognitive performancelevels. Bright artificial light can be used in a number of therapeuticapplications, such as in the treatment of seasonal affective disorder(SAD), certain sleep problems, depression, jet lag, sleep disturbancesin those with Parkinson's disease, the health consequences associatedwith shift work, and the resetting of the human circadian clock.Artificial lighting may change natural processes, interfere withmelatonin production, or disrupt the circadian rhythm. Blue light mayhave a greater tendency than other colored light to affect livingorganisms through the disruption of their biological processes which canrely upon natural cycles of daylight and darkness. Exposure to bluelight late in the evening and at night may be detrimental to one'shealth.

Significant challenges remain in providing LED lamps that can providewhite light across a range of CCT values while simultaneously achievinghigh efficiencies, high luminous flux, good color rendering, andacceptable color stability. It is also a challenge to provide lightingapparatuses that can provide desirable lighting performance whileallowing for the control of circadian energy performance.

DISCLOSURE

The present disclosure provides aspects of methods of generating whitelight with tunable circadian energy performance. The methods cancomprise producing light from the blue, red, yellow/green, and cyanchannels described herein, in various combinations of two or more of thechannels at any given time. The methods comprise producing light from afirst light emitting diode (“LED”) string, producing light from a secondLED string, producing light from a third LED string, a fourth LEDstring, or both the third LED string and the fourth LED string, passingthe light produced by each of the first, second, third, and fourth LEDstrings through one of a plurality of respective luminophoric mediums,combining the light exiting the plurality of respective luminophoricmediums together into white light, wherein the combined white lightcorresponds to at least one of a plurality of points along a predefinedpath near the black body locus in the 1931 CIE Chromaticity Diagram,wherein one or more of the first, second, third, and fourth LED stringscomprises a ultraviolet or violet LED having a peak wavelength ofbetween about 360 nm and about 430 nm. In some implementations,substantially the same white light, in terms of position on the 1931 CIEchromaticity diagram, can be generated in two or more light emittingmodes. White light can be generated within a 7-step MacAdam ellipse of aplurality of target CCTs selected from between 1800K and 4200K via aplurality of emitting modes, the emitting modes comprising a firstemitting mode, wherein the method comprises producing light from thefirst, second, third, and fourth LED strings; a second emitting mode,wherein the method comprises producing light from the first, second, andthird LED strings but not the fourth LED string; and a third emittingmode, wherein the method comprises producing light from the first,second, and fourth LED strings but not the third LED string. For aparticular target CCT, the white light generated in two of the lightemitting modes can be within about 0.1, about 0.2, about 0.3, about 0.4,about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1.0, about1.5, about 2.0, about 2.5, about 3.0, about 3.5, about 4.0, about 4.5,about 5.0, about 5.5, about 6.0, about 6.5, about 7.0, about 7.5, about8.0, or between about 8.0 and about 10.0 standard deviations of colormatching (SDCM). In preferred embodiments, the white light generated intwo of the light emitting modes at a target CCT is within about 0.1 toabout 3.0 SDCM. In further preferred embodiments, the white lightgenerated in two of the light emitting modes at a target CCT is withinabout 0.1 to about 1.0 SDCM, or more preferably within about 0.1 toabout 0.5 SDCM. For each target CCT, the respective circadian actionfactor values of the white light generated in any two of the first,second, and third emitting modes differ from each other by apredetermined threshold amount. The predetermined threshold amount maybe at least about 5%, 10%, 15%, 20% 25%, 30%, 35%, 40%, 50%, 60%, 70%,80%, 100%, 125%, 150%, 200%, 300%, 400%, or more. In someimplementations, the circadian energy tuning can be achieved betweenemitting modes while generating white light corresponding to a pluralityof points along a predefined path within 7-step MacAdam ellipse of thePlanckian locus with the light generated at each point having one ormore of Ra≥80, R9≥50, and GAIBB≥90. In some instances, the first,second, and third LED strings comprise a ultraviolet or violet LEDhaving a peak wavelength of between about 360 nm and about 430 nm andthe fourth LED string comprises a cyan LED having a peak wavelength ofbetween about 485 nm and about 520 nm.

The general disclosure and the following further disclosure areexemplary and explanatory only and are not restrictive of thedisclosure, as defined in the appended claims. Other aspects of thepresent disclosure will be apparent to those skilled in the art in viewof the details as provided herein. In the figures, like referencenumerals designate corresponding parts throughout the different views.All callouts and annotations are hereby incorporated by this referenceas if fully set forth herein.

DRAWINGS

The summary, as well as the following detailed description, is furtherunderstood when read in conjunction with the appended drawings. For thepurpose of illustrating the disclosure, there are shown in the drawingsexemplary implementations of the disclosure; however, the disclosure isnot limited to the specific methods, compositions, and devicesdisclosed. In addition, the drawings are not necessarily drawn to scale.In the drawings:

FIG. 1 illustrates aspects of light emitting devices according to thepresent disclosure;

FIG. 2 illustrates aspects of light emitting devices according to thepresent disclosure;

FIG. 3 depicts a graph of a 1931 CIE Chromaticity Diagram illustratingthe location of the Planckian locus;

FIGS. 4A-4D illustrate some aspects of light emitting devices accordingto the present disclosure, including some suitable color ranges forlight generated by components of the devices;

FIG. 5 illustrates some aspects of light emitting devices according tothe present disclosure, including some suitable color ranges for lightgenerated by components of the devices;

FIG. 6 illustrates some aspects of light emitting devices according tothe present disclosure, including some suitable color ranges for lightgenerated by components of the devices;

FIGS. 7-8 are tables of data of relative spectral power versuswavelength regions for some suitable color points of light generated bycomponents of devices of the present disclosure;

FIGS. 9A-9D are tables of data of color rendering characteristics of animplementation of the present disclosure;

FIG. 10A-10D are tables of data of color rendering characteristics of animplementation of the present disclosure;

FIG. 11A-11D are tables of data of color rendering characteristics of animplementation of the present disclosure;

FIG. 12A-12D are tables of data of color rendering characteristics of animplementation of the present disclosure;

FIG. 13A-13D are tables of data of color rendering characteristics of animplementation of the present disclosure; and

FIG. 14 a table of data of light output of light emitting diodessuitable for implementations of the present disclosure.

All descriptions and callouts in the Figures are hereby incorporated bythis reference as if fully set forth herein.

FURTHER DISCLOSURE

The present disclosure may be understood more readily by reference tothe following detailed description taken in connection with theaccompanying figures and examples, which form a part of this disclosure.It is to be understood that this disclosure is not limited to thespecific devices, methods, applications, conditions or parametersdescribed and/or shown herein, and that the terminology used herein isfor the purpose of describing particular exemplars by way of exampleonly and is not intended to be limiting of the claimed disclosure. Also,as used in the specification including the appended claims, the singularforms “a,” “an,” and “the” include the plural, and reference to aparticular numerical value includes at least that particular value,unless the context clearly dictates otherwise. The term “plurality”, asused herein, means more than one. When a range of values is expressed,another exemplar includes from the one particular value and/or to theother particular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about,” it will be understoodthat the particular value forms another exemplar. All ranges areinclusive and combinable.

It is to be appreciated that certain features of the disclosure whichare, for clarity, described herein in the context of separate exemplar,may also be provided in combination in a single exemplaryimplementation. Conversely, various features of the disclosure that are,for brevity, described in the context of a single exemplaryimplementation, may also be provided separately or in anysubcombination. Further, reference to values stated in ranges includeeach and every value within that range.

In one aspect, the present disclosure provides semiconductor lightemitting devices 100 that can have a plurality of light emitting diode(LED) strings. Each LED string can have one, or more than one, LED. Asdepicted schematically in FIG. 1, the device 100 may comprise one ormore LED strings (101A/101B/101C/101D) that emit light (schematicallyshown with arrows). In some instances, the LED strings can haverecipient luminophoric mediums (102A/102B/102C/102D) associatedtherewith. The light emitted from the LED strings, combined with lightemitted from the recipient luminophoric mediums, can be passed throughone or more optical elements 103. Optical elements 103 may be one ormore diffusers, lenses, light guides, reflective elements, orcombinations thereof.

A recipient luminophoric medium 102A, 102B, 102C, or 102D includes oneor more luminescent materials and is positioned to receive light that isemitted by an LED or other semiconductor light emitting device. In someimplementations, recipient luminophoric mediums include layers havingluminescent materials that are coated or sprayed directly onto asemiconductor light emitting device or on surfaces of the packagingthereof, and clear encapsulants that include luminescent materials thatare arranged to partially or fully cover a semiconductor light emittingdevice. A recipient luminophoric medium may include one medium layer orthe like in which one or more luminescent materials are mixed, multiplestacked layers or mediums, each of which may include one or more of thesame or different luminescent materials, and/or multiple spaced apartlayers or mediums, each of which may include the same or differentluminescent materials. Suitable encapsulants are known by those skilledin the art and have suitable optical, mechanical, chemical, and thermalcharacteristics. In some implementations, encapsulants can includedimethyl silicone, phenyl silicone, epoxies, acrylics, andpolycarbonates. In some implementations, a recipient luminophoric mediumcan be spatially separated (i.e., remotely located) from an LED orsurfaces of the packaging thereof. In some implementations, such spatialsegregation may involve separation of a distance of at least about 1 mm,at least about 2 mm, at least about 5 mm, or at least about 10 mm. Incertain embodiments, conductive thermal communication between aspatially segregated luminophoric medium and one or more electricallyactivated emitters is not substantial. Luminescent materials can includephosphors, scintillators, day glow tapes, nanophosphors, inks that glowin visible spectrum upon illumination with light, semiconductor quantumdots, or combinations thereof. In some implementations, the luminescentmaterials may comprise phosphors comprising one or more of the followingmaterials: BaMg₂Al₁₆O₂₇:Eu²⁺, BaMg₂Al₁₆O₂₇:Eu²⁺,Mn²⁺, CaSiO₃:Pb,Mn,CaWO₄:Pb, MgWO₄, Sr₅Cl(PO₄)₃:Eu²⁺, Sr₂P₂O₇:Sn²⁺, Sr₆P₅BO₂₀:Eu,Ca₅F(PO₄)₃:Sb, (Ba,Ti)₂P₂O₇:Ti, Sr₅F(PO₄)₃:Sb,Mn, (La,Ce,Tb)PO₄:Ce,Tb,(Ca,Zn,Mg)₃(PO₄)₂:Sn, (Sr,Mg)₃(PO₄)₂:Sn, Y₂O₃:Eu³⁺, Mg₄(F)GeO₆:Mn,LaMgAl₁₁O₁₉:Ce, LaPO₄:Ce, SrAl₁₂O₁₉:Ce, BaSi₂O₅:Pb, SrB₄O₇:Eu,Sr₂MgSi₂O₇:Pb, Gd₂O₂S:Tb, Gd₂O₂S:Eu, Gd₂O₂S:Pr, Gd₂O₂S:Pr,Ce,F,Y₂O₂S:Tb, Y₂O₂S:Eu, Y₂O₂S:Pr, Zn(0.5)Cd(0.4)S:Ag, Zn(0.4)Cd(0.6)S:Ag,Y₂SiO₅:Ce, YAlO₃:Ce, Y₃(Al,Ga)₅O₁₂:Ce, CdS:In, ZnO:Ga, ZnO:Zn,(Zn,Cd)S:Cu,Al, ZnCdS:Ag,Cu, ZnS:Ag, ZnS:Cu, NaI:Tl, CsI:Tl,⁶LiF/ZnS:Ag, ⁶LiF/ZnS:Cu,Al,Au, ZnS:Cu,Al, ZnS:Cu,Au,Al, CaAlSiN₃:Eu,(Sr,Ca)AlSiN₃:Eu, (Ba,Ca,Sr,Mg)₂SiO₄:Eu, Lu₃Al₅O₁₂:Ce, Eu³⁺(Gd_(0.9)Y_(0.1))₃Al₅O₁₂:Bi³⁺,Tb³⁺, Y₃Al₅O₁₂:Ce, (La,Y)₃Si₆N₁₁:Ce,Ca₂AlSi₃O₂N₅:Ce³⁺, Ca₂AlSi₃O₂N₅:Eu²⁺, BaMgAl₁₀O₁₇:Eu, Sr₅(PO₄)₃Cl: Eu,(Ba,Ca,Sr,Mg)₂SiO₄:Eu, Si_(6−z)Al_(z)N_(8−z)O_(z):Eu (wherein 0<z≤4.2);M₃Si₆O₁₂N₂:Eu (wherein M=alkaline earth metal element),(Mg,Ca,Sr,Ba)Si₂O₂N₂:Eu, Sr₄Al₁₄O₂₅:Eu, (Ba,Sr,Ca)Al₂O₄:Eu,(Sr,Ba)Al₂Si₂O₈:Eu, (Ba,Mg)₂SiO₄:Eu, (Ba,Sr,Ca)₂(Mg, Zn)Si₂O₇:Eu,(Ba,Ca,Sr,Mg)₉(Sc,Y,Lu,Gd)₂(Si,Ge)₆O₂₄: Eu, Y₂SiO₅:CeTb,Sr₂P₂O₇—Sr₂B₂O₅:Eu, Sr₂Si₃O₈₋₂SrCl₂:Eu, Zn₂SiO₄:Mn, CeMgAl₁₁O₁₉:Tb,Y₃Al₅O₁₂:Tb, Ca₂Y₈(SiO₄)₆O₂:Tb, La₃Ga₅SiO₁₄:Tb,(Sr,Ba,Ca)Ga₂S₄:Eu,Tb,Sm, Y₃(Al,Ga)₅O₁₂:Ce,(Y,Ga,Tb,La,Sm,Pr,Lu)₃(Al,Ga)₅O₁₂:Ce, Ca₃Sc₂Si₃O₁₂:Ce,Ca₃(Sc,Mg,Na,Li)₂Si₃O₁₂:Ce, CaSc₂O₄:Ce, Eu-activated β-Sialon,SrAl₂O₄:Eu, (La,Gd,Y)₂O₂S:Tb, CeLaPO₄:Tb, ZnS:Cu,Al, ZnS:Cu,Au,Al,(Y,Ga,Lu,Sc,La)BO₃:Ce,Tb, Na₂Gd₂B₂O₇:Ce,Tb,(Ba,Sr)₂(Ca,Mg,Zn)B₂O₆:K,Ce,Tb, Ca₈Mg(SiO₄)₄Cl₂:Eu,Mn,(Sr,Ca,Ba)(Al,Ga,In)₂S₄:Eu, (Ca,Sr)₈(Mg,Zn)(SiO₄)₄Cl₂:Eu,Mn,M₃Si₆O₉N₄:Eu, Sr₅Al₅Si₂₁O₂N₃₅:Eu, Sr₃Si₁₃Al₃N₂₁O₂:Eu,(Mg,Ca,Sr,Ba)₂Si₅N₈:Eu, (La,Y)₂O₂S:Eu, (Y,La,Gd,Lu)₂O₂S:Eu, Y(V,P)O₄:Eu,(Ba,Mg)₂SiO₄:Eu,Mn, (Ba,Sr, Ca,Mg)₂SiO₄:Eu,Mn, LiW₂O₈:Eu, LiW₂O₈:Eu,Sm,Eu₂W₂O₉, Eu₂W₂O₉:Nb and Eu₂W₂O₉:Sm, (Ca,Sr)S:Eu, YAlO₃:Eu,Ca₂Y₈(SiO₄)₆O₂:Eu, LiY₉(SiO₄)₆O₂:Eu, (Y,Gd)₃Al₅O₁₂:Ce,(Tb,Gd)₃Al₅O₁₂:Ce, (Mg,Ca,Sr,Ba)₂Si₅(N,O)₈:Eu, (Mg,Ca,Sr,Ba)Si(N,O)₂:Eu,(Mg,Ca,Sr,Ba)AlSi(N,O)₃:Eu, (Sr,Ca,Ba,Mg)₁₀(PO₄)₆Cl₂:Eu, Mn,Eu,Ba₃MgSi₂O₈:Eu,Mn, (Ba,Sr,Ca,Mg)₃(Zn,Mg)Si₂O₈:Eu,Mn,(k−x)MgO.xAF₂.GeO₂:yMn⁴⁺ (wherein k=2.8 to 5, x=0.1 to 0.7, y=0.005 to0.015, A=Ca, Sr, Ba, Zn or a mixture thereof), Eu-activated α-Sialon,(Gd,Y,Lu,La)₂O₃:Eu, Bi, (Gd,Y,Lu,La)₂O₂S:Eu,Bi, (Gd,Y,Lu,La)VO₄:Eu,Bi,SrY₂S₄:Eu,Ce, CaLa₂S₄:Ce,Eu, (Ba,Sr,Ca)MgP₂O₇:Eu, Mn,(Sr,Ca,Ba,Mg,Zn)₂P₂O₇:Eu,Mn, (Y,Lu)₂WO₆:Eu,Ma,(Ba,Sr,Ca)_(x)Si_(y)N_(z):Eu,Ce (wherein x, y and z are integers equalto or greater than 1), (Ca,Sr,Ba,Mg)₁₀(PO₄)₆(F,Cl,Br,OH):Eu,Mn,((Y,Lu,Gd,Tb)_(1−x−y)Sc_(x)Ce_(y))₂(Ca,Mg)(Mg,Zn)_(2+r)Si_(z−q)Ge_(q)O_(12+δ),SrAlSi₄N₇, Sr₂Al₂Si₉O₂N₁₄:Eu, M¹ _(a)M² _(b)M³ _(c)O_(d) (whereinM¹=activator element including at least Ce, M²=bivalent metal element,M³=trivalent metal element, 0.0001≤a≤0.2, 0.8≤b≤1.2, 1.6≤c≤2.4 and3.2≤d≤4.8), A_(2+x)M_(y)Mn_(z)F_(n) (wherein A=Na and/or K; M=Si and Al,and −1≤x≤1, 0.9≤y+z≤1.1, 0.001≤z≤0.4 and 5≤n≤7), KSF/KSNAF, or(La_(1−x−y), Eu_(x), Ln_(y))₂O₂S (wherein 0.02≤x≤0.50 and 0≤y≤0.50,Ln=Y³⁺, Gd³⁺, Lu³⁺, Sc³⁺, Sm³⁺ or Er³⁺). In some preferredimplementations, the luminescent materials may comprise phosphorscomprising one or more of the following materials: CaAlSiN₃:Eu,(Sr,Ca)AlSiN₃:Eu, BaMgAl₁₀O₁₇:Eu, (Ba,Ca,Sr,Mg)₂SiO₄:Eu, β-SiAlON,Lu₃Al₅O₁₂:Ce, Eu³⁺(Cd_(0.9)Y_(0.1))₃Al₅O₁₂:Bi³⁺,Tb³⁺, Y₃Al₅O₁₂:Ce,La₃Si₆N₁₁:Ce, (La,Y)₃Si₆N₁₁:Ce, Ca₂AlSi₃O₂N₅:Ce³⁺,Ca₂AlSi₃O₂N₅:Ce³⁺,Eu²⁺, Ca₂AlSi₃O₂N₅:Eu²⁺, BaMgAl₁₀O₁₇:Eu²⁺,Sr_(4.5)Eu_(0.5)(PO₄)₃Cl, or M¹ _(a)M² _(b)M³ _(c)O_(d) (whereinM¹=activator element comprising Ce, M²=bivalent metal element,M³=trivalent metal element, 0.0001≤a≤0.2, 0.8≤b≤1.2, 1.6≤c≤2.4 and3.2≤d≤4.8). In further preferred implementations, the luminescentmaterials may comprise phosphors comprising one or more of the followingmaterials: CaAlSiN₃:Eu, BaMgAl₁₀O₁₇:Eu, Lu₃Al₅O₁₂:Ce, or Y₃Al₅O₁₂:Ce.

Some implementations of the present invention relate to use of solidstate emitter packages. A solid state emitter package typically includesat least one solid state emitter chip that is enclosed with packagingelements to provide environmental and/or mechanical protection, colorselection, and light focusing, as well as electrical leads, contacts ortraces enabling electrical connection to an external circuit.Encapsulant material, optionally including luminophoric material, may bedisposed over solid state emitters in a solid state emitter package.Multiple solid state emitters may be provided in a single package. Apackage including multiple solid state emitters may include at least oneof the following: a single leadframe arranged to conduct power to thesolid state emitters, a single reflector arranged to reflect at least aportion of light emanating from each solid state emitter, a singlesubmount supporting each solid state emitter, and a single lens arrangedto transmit at least a portion of light emanating from each solid stateemitter. Individual LEDs or groups of LEDs in a solid state package(e.g., wired in series) may be separately controlled. As depictedschematically in FIG. 2, multiple solid state packages 200 may bearranged in a single semiconductor light emitting device 100. Individualsolid state emitter packages or groups of solid state emitter packages(e.g., wired in series) may be separately controlled. Separate controlof individual emitters, groups of emitters, individual packages, orgroups of packages, may be provided by independently applying drivecurrents to the relevant components with control elements known to thoseskilled in the art. In one embodiment, at least one control circuit 201a may include a current supply circuit configured to independently applyan on-state drive current to each individual solid state emitter, groupof solid state emitters, individual solid state emitter package, orgroup of solid state emitter packages. Such control may be responsive toa control signal (optionally including at least one sensor 202 arrangedto sense electrical, optical, and/or thermal properties and/orenvironmental conditions), and a control system 203 may be configured toselectively provide one or more control signals to the at least onecurrent supply circuit. In various embodiments, current to differentcircuits or circuit portions may be pre-set, user-defined, or responsiveto one or more inputs or other control parameters. The design andfabrication of semiconductor light emitting devices are well known tothose skilled in the art, and hence further description thereof will beomitted. Unless otherwise defined, terms used herein should be construedto have the same meaning as commonly understood by one of ordinary skillin the art to which this invention belongs. It will be furtherunderstood that terms used herein should be interpreted as having ameaning that is consistent with their meaning in the context of thisspecification and the relevant art, and should not be interpreted in anidealized or overly formal sense unless expressly so defined herein.

FIG. 3 illustrates a 1931 International Commission on Illumination (CIE)chromaticity diagram. The 1931 CIE Chromaticity diagram is atwo-dimensional chromaticity space in which every visible color isrepresented by a point having x- and y-coordinates. Fully saturated(monochromatic) colors appear on the outer edge of the diagram, whileless saturated colors (which represent a combination of wavelengths)appear on the interior of the diagram. The term “saturated”, as usedherein, means having a purity of at least 85%, the term “purity” havinga well-known meaning to persons skilled in the art, and procedures forcalculating purity being well-known to those of skill in the art. ThePlanckian locus, or black body locus (BBL), represented by line 150 onthe diagram, follows the color an incandescent black body would take inthe chromaticity space as the temperature of the black body changes fromabout 1000K to 10,000 K. The black body locus goes from deep red at lowtemperatures (about 1000 K) through orange, yellowish white, white, andfinally bluish white at very high temperatures. The temperature of ablack body radiator corresponding to a particular color in achromaticity space is referred to as the “correlated color temperature.”In general, light corresponding to a correlated color temperature (CCT)of about 2700 K to about 6500 K is considered to be “white” light. Inparticular, as used herein, “white light” generally refers to lighthaving a chromaticity point that is within a 10-step MacAdam ellipse ofa point on the black body locus having a CCT between 2700K and 6500K.However, it will be understood that tighter or looser definitions ofwhite light can be used if desired. For example, white light can referto light having a chromaticity point that is within a seven step MacAdamellipse of a point on the black body locus having a CCT between 2700Kand 6500K. The distance from the black body locus can be measured in theCIE 1960 chromaticity diagram, and is indicated by the symbol Δuv, orDUV. If the chromaticity point is above the Planckian locus the DUV isdenoted by a positive number; if the chromaticity point is below thelocus, DUV is indicated with a negative number. If the DUV issufficiently positive, the light source may appear greenish or yellowishat the same CCT. If the DUV is sufficiently negative, the light sourcecan appear to be purple or pinkish at the same CCT. Observers may preferlight above or below the Planckian locus for particular CCT values. DUVcalculation methods are well known by those of ordinary skill in the artand are more fully described in ANSI C78.377, American National Standardfor Electric Lamps—Specifications for the Chromaticity of Solid StateLighting (SSL) Products, which is incorporated by reference herein inits entirety for all purposes. A point representing the CIE StandardIlluminant D65 is also shown on the diagram. The D65 illuminant isintended to represent average daylight and has a CCT of approximately6500K and the spectral power distribution is described more fully inJoint ISO/CIE Standard, ISO 10526:1999/CIE 5005/E-1998, CIE StandardIlluminants for Colorimetry, which is incorporated by reference hereinin its entirety for all purposes.

The light emitted by a light source may be represented by a point on achromaticity diagram, such as the 1931 CIE chromaticity diagram, havingcolor coordinates denoted (ccx, ccy) on the X-Y axes of the diagram. Aregion on a chromaticity diagram may represent light sources havingsimilar chromaticity coordinates.

The ability of a light source to accurately reproduce color inilluminated objects can be characterized using the color rendering index(“CRI”), also referred to as the CIE Ra value. The Ra value of a lightsource is a modified average of the relative measurements of how thecolor rendition of an illumination system compares to that of areference black-body radiator or daylight spectrum when illuminatingeight reference colors R1-R8. Thus, the Ra value is a relative measureof the shift in surface color of an object when lit by a particularlamp. The Ra value equals 100 if the color coordinates of a set of testcolors being illuminated by the illumination system are the same as thecoordinates of the same test colors being irradiated by a referencelight source of equivalent CCT. For CCTs less than 5000K, the referenceilluminants used in the CRI calculation procedure are the SPDs ofblackbody radiators; for CCTs above 5000K, imaginary SPDs calculatedfrom a mathematical model of daylight are used. These reference sourceswere selected to approximate incandescent lamps and daylight,respectively. Daylight generally has an Ra value of nearly 100,incandescent bulbs have an Ra value of about 95, fluorescent lightingtypically has an Ra value of about 70 to 85, while monochromatic lightsources have an Ra value of essentially zero. Light sources for generalillumination applications with an Ra value of less than 50 are generallyconsidered very poor and are typically only used in applications whereeconomic issues preclude other alternatives. The calculation of CIE Ravalues is described more fully in Commission Internationale del'Éclairage. 1995. Technical Report: Method of Measuring and SpecifyingColour Rendering Properties of Light Sources, CIE No. 13.3-1995. Vienna,Austria: Commission Internationale de l'Éclairage, which is incorporatedby reference herein in its entirety for all purposes. In addition to theRa value, a light source can also be evaluated based on a measure of itsability to render a saturated red reference color R9 with the R9 colorrendering value (“R9 value”). Light sources can further be evaluated bycalculating the gamut area index (“GAI”). Connecting the rendered colorpoints from the determination of the CIE Ra value in two dimensionalspace will form a gamut area. Gamut area index is calculated by dividingthe gamut area formed by the light source with the gamut area formed bya reference source using the same set of colors that are used for CRI.GAI uses an Equal Energy Spectrum as the reference source rather than ablack body radiator. A gamut area index related to a black body radiator(“GAIBB”) can be calculated by using the gamut area formed by theblackbody radiator at the equivalent CCT to the light source.

The ability of a light source to accurately reproduce color inilluminated objects can be characterized using the metrics described inIES Method for Evaluating Light Source Color Rendition, IlluminatingEngineering Society, Product ID: TM-30-15 (referred to herein as the“TM-30-15 standard”), which is incorporated by reference herein in itsentirety for all purposes. The TM-30-15 standard describes metricsincluding the Fidelity Index (Rf) and the Gamut Index (Rg) that can becalculated based on the color rendition of a light source for 99 colorevaluation samples (“CES”). The 99 CES provide uniform color spacecoverage, are intended to be spectral sensitivity neutral, and providecolor samples that correspond to a variety of real objects. Rf valuesrange from 0 to 100 and indicate the fidelity with which a light sourcerenders colors as compared with a reference illuminant. Rg valuesprovide a measure of the color gamut that the light source providesrelative to a reference illuminant. The range of Rg depends upon the Rfvalue of the light source being tested. The reference illuminant isselected depending on the CCT. For CCT values less than or equal to4500K, Planckian radiation is used. For CCT values greater than or equalto 5500K, CIE Daylight illuminant is used. Between 4500K and 5500K aproportional mix of Planckian radiation and the CIE Daylight illuminantis used, according to the following equation:

${{S_{r,M}\left( {\lambda,T_{t}} \right)} = {{\frac{5500 - T_{t}}{1000}{S_{r,P}\left( {\lambda,T_{t}} \right)}} + {\left( {1 - \frac{5500 - T_{t}}{1000}} \right){S_{r,D}\left( {\lambda,T_{t}} \right)}}}},$

where T_(t) is the CCT value, S_(r,M)(λ,T_(t)) is the proportional mixreference illuminant, S_(r,P)(λ,T_(t)) is Planckian radiation, andS_(r,D)(λ,T_(t)) is the CIE Daylight illuminant.

The ability of a light source to provide illumination that allows forthe clinical observation of cyanosis is based upon the light source'sspectral power density in the red portion of the visible spectrum,particularly around 660 nm. The cyanosis observation index (“COI”) isdefined by AS/NZS 1680.2.5 Interior Lighting Part 2.5: Hospital andMedical Tasks, Standards Australia, 1997 which is incorporated byreference herein in its entirety, including all appendices, for allpurposes. COI is applicable for CCTs from about 3300K to about 5500K,and is preferably of a value less than about 3.3. If a light source'soutput around 660 nm is too low a patient's skin color may appear darkerand may be falsely diagnosed as cyanosed. If a light source's output at660 nm is too high, it may mask any cyanosis, and it may not bediagnosed when it is present. COI is a dimensionless number and iscalculated from the spectral power distribution of the light source. TheCOI value is calculated by calculating the color difference betweenblood viewed under the test light source and viewed under the referencelamp (a 4000 K Planckian source) for 50% and 100% oxygen saturation andaveraging the results. The lower the value of COI, the smaller the shiftin color appearance results under illumination by the source underconsideration.

The ability of a light source to accurately reproduce color inilluminated objects can be characterized by the Television LightingConsistency Index (“TLCI-2012” or “TLCI”) value Qa, as described fullyin EBU Tech 3355, Method for the Assessment of the ColorimetricProperties of Luminaires, European Broadcasting Union (“EBU”), Geneva,Switzerland (2014), and EBU Tech 3355-s1, An Introduction toSpectroradiometry, which are incorporated by reference herein in theirentirety, including all appendices, for all purposes. The TLCI comparesthe test light source to a reference luminaire, which is specified to beone whose chromaticity falls on either the Planckian or Daylight locusand having a color temperature which is that of the CCT of the testlight source. If the CCT is less than 3400 K, then a Planckian radiatoris assumed. If the CCT is greater than 5000 K, then a Daylight radiatoris assumed. If the CCT lies between 3400 K and 5000 K, then a mixedilluminant is assumed, being a linear interpolation between Planckian at3400 K and Daylight at 5000 K. Therefore, it is necessary to calculatespectral power distributions for both Planckian and Daylight radiators.The mathematics for both operations is known in the art and is describedmore fully in CIE Technical Report 15:2004, Colorimetry 3^(rd) ed.,International Commission on Illumination (2004), which is incorporatedherein in its entirety for all purposes.

In some aspects the present disclosure relates to lighting devices andmethods to provide light having particular vision energy and circadianenergy performance. Many figures of merit are known in the art, some ofwhich are described in Ji Hye Oh, Su Ji Yang and Young Rag Do, “Healthy,natural, efficient and tunable lighting: four-package white LEDs foroptimizing the circadian effect, color quality and vision performance,”Light: Science & Applications (2014) 3: e141-e149, which is incorporatedherein in its entirety, including supplementary information, for allpurposes. Luminous efficacy of radiation (“LER”) can be calculated fromthe ratio of the luminous flux to the radiant flux (S(λ)), i.e. thespectral power distribution of the light source being evaluated, withthe following equation:

${{LER}\left( \frac{lm}{W} \right)} = {683\left( \frac{lm}{W} \right){\frac{\int{{V(\lambda)}{S(\lambda)}d\; \lambda}}{\int{{S(\lambda)}d\; \lambda}}.}}$

Circadian efficacy of radiation (“CER”) can be calculated from the ratioof circadian luminous flux to the radiant flux, with the followingequation:

${{CER}\left( \frac{blm}{W} \right)} = {683\left( \frac{blm}{W} \right){\frac{\int{{C(\lambda)}{S(\lambda)}d\; \lambda}}{\int{{S(\lambda)}d\; \lambda}}.}}$

Circadian action factor (“CAF”) can be defined by the ratio of CER toLER, with the following equation:

$\left( \frac{blm}{lm} \right) = {\frac{{CER}\left( \frac{blm}{W} \right)}{{LER}\left( \frac{lm}{W} \right)}.}$

The term “blm” refers to biolumens, units for measuring circadian flux,also known as circadian lumens. The term “lm” refers to visual lumens.V(λ) is the photopic spectral luminous efficiency function and C(λ) isthe circadian spectral sensitivity function. The calculations herein usethe circadian spectral sensitivity function, C(λ), from Gall et al.,Proceedings of the CIE Symposium 2004 on Light and Health: Non-VisualEffects, 30 Sep.-2 Oct. 2004; Vienna, Austria 2004. CIE: Wien, 2004, pp129-132, which is incorporated herein in its entirety for all purposes.By integrating the amount of light (milliwatts) within the circadianspectral sensitivity function and dividing such value by the number ofphotopic lumens, a relative measure of melatonin suppression effects ofa particular light source can be obtained. A scaled relative measuredenoted as melatonin suppressing milliwatts per hundred lumens may beobtained by dividing the photopic lumens by 100. The term “melatoninsuppressing milliwatts per hundred lumens” consistent with the foregoingcalculation method is used throughout this application and theaccompanying figures and tables.

In some exemplary implementations, the present disclosure providessemiconductor light emitting devices 100 that include a plurality of LEDstrings, with each LED string having a recipient luminophoric mediumthat comprises a luminescent material. The LED(s) in each string and theluminophoric medium in each string together emit an unsaturated lighthaving a color point within a color range in the 1931 CIE chromaticitydiagram. A “color range” in the 1931 CIE chromaticity diagram refers toa bounded area defining a group of color coordinates (ccx, ccy).

In some implementations, four LED strings (101A/101B/101C/101D) arepresent in a device 100, and the LED strings can have recipientluminophoric mediums (102A/102B/102C/102D). A first LED string 101A anda first luminophoric medium 102A together can emit a first light havinga first color point within a blue color range. The combination of thefirst LED string 101A and the first luminophoric medium 102A are alsoreferred to herein as a “blue channel.” A second LED string 101B and asecond luminophoric medium 102B together can emit a second light havinga second color point within a red color range. The combination of thesecond LED string 101A and the second luminophoric medium 102A are alsoreferred to herein as a “red channel.” A third LED string 101C and athird luminophoric medium 102C together can emit a third light having athird color point within a yellow/green color range. The combination ofthe third LED string 101A and the third luminophoric medium 102A arealso referred to herein as a “yellow/green channel.” A fourth LED string101D and a fourth luminophoric medium 102D together can emit a fourthlight having a fourth color point within a cyan color range. Thecombination of the fourth LED string 101A and the fourth luminophoricmedium 102A are also referred to herein as a “cyan channel.” The first,second, third, and fourth LED strings 101A/101B/101C/101D can beprovided with independently applied on-state drive currents in order totune the intensity of the first, second, third, and fourth unsaturatedlight produced by each string and luminophoric medium together. Byvarying the drive currents in a controlled manner, the color coordinate(ccx, ccy) of the total light that is emitted from the device 100 can betuned. In some implementations, the device 100 can provide light atsubstantially the same color coordinate with different spectral powerdistribution profiles, which can result in different lightcharacteristics at the same CCT. In some implementations, white lightcan be generated in modes that only produce light from two or three ofthe LED strings. In one implementation, white light is generated usingonly the first, second, and third LED strings, i.e. the blue, red, andyellow/green channels. In another implementation, white light isgenerated using only the first, second, and fourth LED strings, i.e.,the blue, red, and cyan channels. In some implementations, only two ofthe LED strings are producing light during the generation of whitelight, as the other two LED strings are not necessary to generate whitelight at the desired color point with the desired color renderingperformance.

In some implementations, the first color point within a blue color rangecan be generated using a first LED string driven by a plurality of blueLEDs with at least two different peak emission wavelengths. In somepreferred implementations, two different blue LEDs are used in thedevice, having 1931 CIE chromaticity diagram color points of (0.1574,0.0389) and (0.1310, 0.0651) and having peak emission wavelengths ofapproximately 450 nm to approximately 455 nm and approximately 460 nm toapproximately 465 nm, respectively. In some implementations two or moredifferent LEDs in the first LED string can utilize different recipientluminophoric mediums. In other implementations, two or more differentLEDs in the first LED string can utilize a common recipient luminophoricmedium. The plurality of LEDs and the one or more recipient luminophoricmediums can generate a combined emission of a blue color point withinthe suitable ranges 301A-C described elsewhere herein.

FIGS. 4A, 4B, 4C, and 4D depict suitable color ranges for someimplementations of the disclosure. FIG. 4A depicts a cyan color range304A defined by a line connecting the ccx, ccy color coordinates (0.18,0.55) and (0.27, 0.72), the constant CCT line of 9000K, the Planckianlocus between 9000K and 4600K, the constant CCT line of 4600K, and thespectral locus. FIG. 4B depicts a yellow/green color range 303A definedby the constant CCT line of 4600K, the Planckian locus between 4600K and550K, the spectral locus, and a line connecting the ccx, ccy colorcoordinates (0.445, 0.555) and (0.38, 0.505). FIG. 4C depicts a bluecolor range 301A defined by a line connecting the ccx, ccy colorcoordinates of the infinity point of the Planckian locus (0.242, 0.24)and (0.12, 0.068), the Planckian locus from 4000K and infinite CCT, theconstant CCT line of 4000K, the line of purples, and the spectral locus.FIG. 4D depicts a red color range 302A defined by the spectral locusbetween the constant CCT line of 1600K and the line of purples, the lineof purples, a line connecting the ccx, ccy color coordinates (0.61,0.21) and (0.47, 0.28), and the constant CCT line of 1600K. It should beunderstood that any gaps or openings in the described boundaries for thecolor ranges 301A, 302A, 303A, 304A should be closed with straight linesto connect adjacent endpoints in order to define a closed boundary foreach color range.

In some implementations, suitable color ranges can be narrower thanthose depicted in FIGS. 4A-4D. FIG. 5 depicts some suitable color rangesfor some implementations of the disclosure. A blue color range 301B canbe defined by a 60-step MacAdam ellipse at a CCT of 20000K, 40 pointsbelow the Planckian locus. A red color range 302B can be defined by a20-step MacAdam ellipse at a CCT of 1200K, 20 points below the Planckianlocus. A yellow/green color range 303B can be defined by a 16-stepMacAdam ellipse at a CCT of 3700K, 30 points above Planckian locus. Acyan color range 304B can be defined by 30-step MacAdam ellipse at a CCTof 6000K, 68 points above the Planckian locus. FIG. 6 depicts somefurther color ranges suitable for some implementations of thedisclosure: blue color range 301C, red color range 302C, yellow/greencolor range 303C, and cyan color range 304C.

In some implementations, the LEDs in the first, second, third and fourthLED strings can be LEDs with peak emission wavelengths at or below about535 nm. In some implementations, the LEDs emit light with peak emissionwavelengths between about 360 nm and about 535 nm. In someimplementations, the LEDs in the first, second, third and fourth LEDstrings can be formed from InGaN semiconductor materials. In somepreferred implementations, the first, second, and third LED strings canhave LEDs having a peak wavelength between about 405 nm and about 485nm. In some implementations the fourth LED string can have LEDs having apeak wavelength between about 485 nm and about 520 nm. The LEDs used inthe first, second, third, and fourth LED strings may have full-widthhalf-maximum wavelength ranges of between about 10 nm and about 30 nm.In some preferred implementations, the first, second, and third LEDstrings can include one or more LUXEON Z Color Line royal blue LEDs(product code LXZ1-PR01) of color bin codes 3, 4, 5, or 6 or one or moreLUXEON Z Color Line blue LEDs (LXZ1-PB01) of color bin code 1 or 2(Lumileds Holding B.V., Amsterdam, Netherlands). In some preferredimplementations, the fourth LED string can have one or more LUXEON ZColor Line blue LEDs (LXZ1-PB01) of color bin code 5 or one or moreLUXEON Z Color Line cyan LEDs (LXZ1-PE01) color bin code 1, 2, 6, 7, 8,or 9 (Lumileds Holding B.V., Amsterdam, Netherlands). The wavelengthinformation for these color bins is provided in the table in FIG. 14.Similar LEDs from other manufacturers such as OSRAM GmbH and Cree, Inc.could also be used, provided they have peak emission and full-widthhalf-maximum wavelengths of the appropriate values.

In some implementations, the LEDs in one or more of the first, second,third and fourth LED strings can be LEDs with peak emission wavelengthsat or below about 535 nm. In some implementations, the LEDs in one ormore of the first, second, third and fourth LED strings can emit lightwith peak emission wavelengths between about 360 nm and about 430 nm. Insome implementations, the LEDs can be GaN based LEDs. GaN based LEDchips can include a sapphire substrate, a buffer layer, an n-type GaNlayer, active layer with multiple quantum well (MQW) therein, p-type GaNlayer, a first electrode, and a second electrode. In otherimplementations LEDs that emit light with peak emission wavelengthsbetween about 360 nm and about 430 nm can be LUXEON FlipChip UV orLUXEON Z UV LEDs from Lumileds Holding B.V., Amsterdam, Netherlands. Insome preferred implementations, the first, second, and third LED stringscan have LEDs having a peak wavelength between about 360 nm and about430 nm, and the fourth LED string can have LEDs having a peak wavelengthbetween about 485 nm and about 520 nm.

In implementations utilizing LEDs that emit substantially saturatedlight at wavelengths between about 360 nm and about 535 nm, the device100 can include suitable recipient luminophoric mediums for each LED inorder to produce light having color points within the suitable bluecolor ranges 301A-C, red color ranges 302A-C, yellow/green color ranges303A-C, and cyan color ranges 304A-C described herein. The light emittedby each LED string, i.e., the light emitted from the LED(s) andassociated recipient luminophoric medium together, can have a spectralpower distribution (“SPD”) having spectral power with ratios of poweracross the visible wavelength spectrum from about 380 nm to about 780nm. While not wishing to be bound by any particular theory, it isspeculated that the use of such LEDs in combination with recipientluminophoric mediums to create unsaturated light within the suitablecolor ranges 301A-C, 302A-C, 303A-C, and 304A-C provides for improvedcolor rendering performance for white light across a predetermined rangeof CCTs from a single device 100. Some suitable ranges for spectralpower distribution ratios of the light emitted by the four LED strings(101A/101B/101C/101D) and recipient luminophoric mediums(102A/102B/102C/102D) together are shown in FIGS. 7 and 8. The figuresshow the ratios of spectral power within wavelength ranges, with anarbitrary reference wavelength range selected for each color range andnormalized to a value of 100.0. FIGS. 7 and 8 show suitable minimum andmaximum values for the spectral intensities within various rangesrelative to the normalized range with a value of 100.0, for the colorpoints within the blue, cyan, yellow/green (“yag”), and red colorranges. While not wishing to be bound by any particular theory, it isspeculated that because the spectral power distributions for generatedlight with color points within the blue, cyan, and yellow/green colorranges contains higher spectral intensity across visible wavelengths ascompared to lighting apparatuses and methods that utilize more saturatedcolors, this allows for improved color rendering for test colors otherthan R1-R8.

Blends of luminescent materials can be used in luminophoric mediums(102A/102B/102C/102D) to create luminophoric mediums having the desiredsaturated color points when excited by their respective LED strings(101A/101B/101C/101D) including luminescent materials such as thosedisclosed in co-pending application PCT/US2016/015318 filed Jan. 28,2016, entitled “Compositions for LED light conversion,” the entirety ofwhich is hereby incorporated by this reference as if sully set forthherein. Traditionally desired combined output light can be generatedalong a tie line between the LED string output light color point and thesaturated color point of the associated recipient luminophoric medium byutilizing different ratios of total luminescent material to theencapsulant material in which it is incorporated. Increasing the amountof luminescent material in the optical path will shift the output lightcolor point towards the saturated color point of the luminophoricmedium. In some instances, the desired saturated color point of arecipient luminophoric medium can be achieved by blending two or moreluminescent materials in a ratio. The appropriate ratio to achieve thedesired saturated color point can be determined via methods known in theart. Generally speaking, any blend of luminescent materials can betreated as if it were a single luminescent material, thus the ratio ofluminescent materials in the blend can be adjusted to continue to meet atarget CIE value for LED strings having different peak emissionwavelengths. Luminescent materials can be tuned for the desiredexcitation in response to the selected LEDs used in the LED strings(101A/101B/101C/101D), which may have different peak emissionwavelengths within the range of from about 360 nm to about 535 nm.Suitable methods for tuning the response of luminescent materials areknown in the art and may include altering the concentrations of dopantswithin a phosphor, for example.

In some implementations of the present disclosure, luminophoric mediumscan be provided with combinations of two types of luminescent materials.The first type of luminescent material emits light at a peak emissionbetween about 515 nm and about 590 nm in response to the associated LEDstring emission. The second type of luminescent material emits at a peakemission between about 590 nm and about 700 nm in response to theassociated LED string emission. In some instances, the luminophoricmediums disclosed herein can be formed from a combination of at leastone luminescent material of the first and second types described in thisparagraph. In implementations, the luminescent materials of the firsttype can emit light at a peak emission at about 515 nm, 525 nm, 530 nm,535 nm, 540 nm, 545 nm, 550 nm, 555 nm, 560 nm, 565 nm, 570 nm, 575 nm,580 nm, 585 nm, or 590 nm in response to the associated LED stringemission. In preferred implementations, the luminescent materials of thefirst type can emit light at a peak emission between about 520 nm toabout 555 nm. In implementations, the luminescent materials of thesecond type can emit light at a peak emission at about 590 nm, about 595nm, 600 nm, 605 nm, 610 nm, 615 nm, 620 nm, 625 nm, 630 nm, 635 nm, 640nm, 645 nm, 650 nm, 655 nm, 670 nm, 675 nm, 680 nm, 685 nm, 690 nm, 695nm, or 670 nm in response to the associated LED string emission. Inpreferred implementations, the luminescent materials of the first typecan emit light at a peak emission between about 600 nm to about 670 nm.Some exemplary luminescent materials of the first and second type aredisclosed elsewhere herein and referred to as Compositions A-F. Table 1shows aspects of some exemplar luminescent materials and properties:

TABLE 1 Emission Emission Peak FWHM Density Peak FWHM Range RangeDesignator Exemplary Material(s) (g/mL) (nm) (nm) (nm) (nm) CompositionLuag: Cerium doped 6.73 535 95 530-540  90-100 “A” lutetium aluminumgarnet (Lu₃Al₅O₁₂) Composition Yag: Cerium doped yttrium 4.7 550 110545-555 105-115 “B” aluminum garnet (Y₃Al₅O₁₂) Composition a 650 nm-peakwavelength 3.1 650 90 645-655 85-95 “C” emission phosphor: Europiumdoped calcium aluminum silica nitride (CaAlSiN₃) Composition a 525nm-peak wavelength 3.1 525 60 520-530 55-65 “D” emission phosphor: GBAM:BaMgAl₁₀O₁₇: Eu Composition a 630 nm-peak wavelength 5.1 630 40 625-63535-45 “E” emission quantum dot: any semiconductor quantum dot materialof appropriate size for desired emission wavelengths Composition a 610nm-peak wavelength 5.1 610 40 605-615 35-45 “F” emission quantum dot:any semiconductor quantum dot material of appropriate size for desiredemission wavelengths

Blends of Compositions A-F can be used in luminophoric mediums(102A/102B/102C/102D) to create luminophoric mediums having the desiredsaturated color points when excited by their respective LED strings(101A/101B/101C/101D). In some implementations, one or more blends ofone or more of Compositions A-F can be used to produce luminophoricmediums (102A/102B/102C/102D). In some preferred implementations, one ormore of Compositions A, B, and D and one or more of Compositions C, E,and F can be combined to produce luminophoric mediums(102A/102B/102C/102D). In some preferred implementations, theencapsulant for luminophoric mediums (102A/102B/102C/102D) comprises amatrix material having density of about 1.1 mg/mm³ and refractive indexof about 1.545. Suitable matrix materials can have refractive indices ofabout 1.4 to about 1.6. In some implementations, Composition A can havea refractive index of about 1.82 and a particle size from about 18micrometers to about 40 micrometers. In some implementations,Composition B can have a refractive index of about 1.84 and a particlesize from about 13 micrometers to about 30 micrometers. In someimplementations, Composition C can have a refractive index of about 1.8and a particle size from about 10 micrometers to about 15 micrometers.In some implementations, Composition D can have a refractive index ofabout 1.8 and a particle size from about 10 micrometers to about 15micrometers. Suitable phosphor materials for Compositions A, B, C, and Dare commercially available from phosphor manufacturers such asMitsubishi Chemical Holdings Corporation (Tokyo, Japan), IntematixCorporation (Fremont, Calif.), EMD Performance Materials of Merck KGaA(Darmstadt, Germany), and PhosphorTech Corporation (Kennesaw, Ga.).

In some aspects, the present disclosure provides methods of generatingwhite light with tunable circadian energy performance. The methods cancomprise producing light from the blue, red, yellow/green, and cyanchannels described herein, in various combinations of two or more of thechannels at any given time. Substantially the same white light, in termsof position on the 1931 CIE chromaticity diagram, can be generated intwo or more light emitting modes. White light can be generated within a7-step MacAdam ellipse of a plurality of target CCTs selected frombetween 1800K and 4200K via a plurality of emitting modes, the emittingmodes comprising a first emitting mode, wherein the method comprisesproducing light from the first, second, third, and fourth LED strings; asecond emitting mode, wherein the method comprises producing light fromthe first, second, and third LED strings but not the fourth LED string;and a third emitting mode, wherein the method comprises producing lightfrom the first, second, and fourth LED strings but not the third LEDstring. For a particular target CCT, the white light generated in two ofthe light emitting modes can be within about 0.1, about 0.2, about 0.3,about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about1.0, about 1.5, about 2.0, about 2.5, about 3.0, about 3.5, about 4.0,about 4.5, about 5.0, about 5.5, about 6.0, about 6.5, about 7.0, about7.5, about 8.0, or between about 8.0 and about 10.0 standard deviationsof color matching (SDCM). In preferred embodiments, the white lightgenerated in two of the light emitting modes at a target CCT is withinabout 0.1 to about 3.0 SDCM. In further preferred embodiments, the whitelight generated in two of the light emitting modes at a target CCT iswithin about 0.1 to about 1.0 SDCM, or more preferably within about 0.1to about 0.5 SDCM. For each target CCT, the respective circadian actionfactor values of the white light generated in any two of the first,second, and third emitting modes differ from each other by apredetermined threshold amount. The predetermined threshold amount maybe at least about 5%, 10%, 15%, 20% 25%, 30%, 35%, 40%, 50%, 60%, 70%,80%, 100%, 125%, 150%, 200%, 300%, 400%, or more. In someimplementations, the circadian energy tuning can be achieved betweenemitting modes while generating white light corresponding to a pluralityof points along a predefined path within 7-step MacAdam ellipse of thePlanckian locus with the light generated at each point having one ormore of Ra≥80, R9≥50, and GAIBB≥90. The first, second, and third LEDstrings can have ultraviolet or violet LEDs having a peak wavelength ofbetween about 360 nm and about 430 nm and the fourth LED string can havea cyan LED having a peak wavelength of between about 485 nm and about520 nm.

EXAMPLES General Simulation Method.

Devices having four LED strings with particular color points weresimulated. For each device, LED strings and recipient luminophoricmediums with particular emissions were selected, and then white lightrendering capabilities were calculated for a select number ofrepresentative points on or near the Planckian locus between about 1800Kand 10000K. The CIE Ra value, R9 value, GAI, and GAIBB were calculatedat each representative point, along with circadian energy performancemetrics.

The calculations were performed with Scilab (Scilab Enterprises,Versailles, France), LightTools (Synopsis, Inc., Mountain View, Calif.),and custom software created using Python (Python Software Foundation,Beaverton, Oreg.). Each LED string was simulated with an LED emissionspectrum and excitation and emission spectra of luminophoric medium(s).For luminophoric mediums comprising phosphors, the simulations alsoincluded the absorption spectrum and particle size of phosphorparticles. The LED strings generating combined emissions within blue,red and yellow/green color regions were prepared using spectra of aLUXEON Z Color Line royal blue LED (product code LXZ1-PR01) of color bincodes 3, 4, 5, or 6 or a LUXEON Z Color Line blue LED (LXZ1-PB01) ofcolor bin code 1 or 2 (Lumileds Holding B.V., Amsterdam, Netherlands).The LED strings generating combined emissions with color points withinthe cyan regions were prepared using spectra of a LUXEON Z Color Lineblue LED (LXZ1-PB01) of color bin code 5 or LUXEON Z Color Line cyan LED(LXZ1-PE01) color bin code 1, 8, or 9 (Lumileds Holding B.V., Amsterdam,Netherlands). FIG. 14 shows emission characteristics of selected LEDsfrom Lumileds. Similar LEDs from other manufacturers such as OSRAM GmbHand Cree, Inc. could also be used.

The emission, excitation and absorption curves are available fromcommercially available phosphor manufacturers such as MitsubishiChemical Holdings Corporation (Tokyo, Japan), Intematix Corporation(Fremont, Calif.), EMD Performance Materials of Merck KGaA (Darmstadt,Germany), and PhosphorTech Corporation (Kennesaw, Ga.). The luminophoricmediums used in the LED strings were combinations of one or more ofCompositions A, B, and D and one or more of Compositions C, E, and F asdescribed more fully elsewhere herein. Those of skill in the artappreciate that various combinations of LEDs and phosphor blends can becombined to generate combined emissions with desired color points on the1931 CIE chromaticity diagram and the desired spectral powerdistributions.

Example 1

A semiconductor light emitting device was simulated having four LEDstrings. A first LED string is driven by a blue LED having peak emissionwavelength of approximately 450 nm to approximately 455 nm, utilizes arecipient luminophoric medium, and generates a combined emission of ablue color point with a 1931 CIE chromaticity diagram color point of(0.2625, 0.1763). A second LED string is driven by a blue LED havingpeak emission wavelength of approximately 450 nm to approximately 455nm, utilizes a recipient luminophoric medium, and generates a combinedemission of a red color point with a 1931 CIE chromaticity diagram colorpoint of (0.5842, 0.3112). A third LED string is driven by a blue LEDhaving peak emission wavelength of approximately 450 nm to approximately455 nm, utilizes a recipient luminophoric medium, and generates acombined emission of a yellow/green color point with a 1931 CIEchromaticity diagram color point of (0.4482, 0.5258). A fourth LEDstring is driven by a cyan LED having a peak emission wavelength ofapproximately 505 nm, utilizes a recipient luminophoric medium, andgenerates a combined emission of a cyan color point with a 1931 CIEchromaticity diagram color point of (0.3258, 0.5407). FIGS. 9A-9C showscolor-rendering characteristics of the device for a representativeselection of white light color points near the Planckian locus, withdata shown for white light generated in different operational modesusing combinations of the first, second, third, and fourth LED strings.FIG. 9D shows comparisons of circadian action factor values for whitelight points generated at similar CCT values under different operationalmodes. Table 2 below shows the spectral power distributions for theblue, red, yellow-green, and cyan color points generated by the deviceof this Example, with spectral power shown within wavelength ranges innanometers from 380 nm to 780 nm, with an arbitrary reference wavelengthrange selected for each color range and normalized to a value of 100.0:

TABLE 2 380-420 421-460 461-500 501-540 541-580 581-620 621-660 661-700701-740 741-780 Blue 0.4 100.0 20.9 15.2 25.3 26.3 25.1 13.9 5.2 1.6 Red0.0 9.6 2.0 1.4 9.0 48.5 100.0 73.1 29.5 9.0 Yellow- 1.0 1.1 5.7 75.8100.0 83.6 69.6 40.9 15.6 4.7 Green Cyan 0.1 0.5 53.0 100.0 65.0 41.623.1 11.6 4.2 0.6

Example 2

A semiconductor light emitting device was simulated having four LEDstrings. A first LED string is driven by a blue LED having peak emissionwavelength of approximately 450 nm to approximately 455 nm, utilizes arecipient luminophoric medium, and generates a combined emission of ablue color point with a 1931 CIE chromaticity diagram color point of(0.2625, 0.1763). A second LED string is driven by a blue LED havingpeak emission wavelength of approximately 450 nm to approximately 455nm, utilizes a recipient luminophoric medium, and generates a combinedemission of a red color point with a 1931 CIE chromaticity diagram colorpoint of (0.5842, 0.3112). A third LED string is driven by a blue LEDhaving peak emission wavelength of approximately 450 nm to approximately455 nm, utilizes a recipient luminophoric medium, and generates acombined emission of a yellow/green color point with a 1931 CIEchromaticity diagram color point of (0.5108, 0.4708). A fourth LEDstring is driven by a cyan LED having a peak emission wavelength ofapproximately 505 nm, utilizes a recipient luminophoric medium, andgenerates a combined emission of a cyan color point with a 1931 CIEchromaticity diagram color point of (0.3258, 0.5407). FIGS. 10A-10Cshows color-rendering characteristics of the device for a representativeselection of white light color points near the Planckian locus, withdata shown for white light generated in different operational modesusing combinations of the first, second, third, and fourth LED strings.FIG. 10D shows comparisons of circadian action factor values for whitelight points generated at similar CCT values under different operationalmodes. Table 3 below shows the spectral power distributions for theblue, red, yellow-green, and cyan color points generated by the deviceof this Example, with spectral power shown within wavelength ranges innanometers from 380 nm to 780 nm, with an arbitrary reference wavelengthrange selected for each color range and normalized to a value of 100.0:

TABLE 3 380-420 421-460 461-500 501-540 541-580 581-620 621-660 661-700701-740 741-780 Blue 0.3 100.0 196.1 33.0 40.3 38.2 34.2 20.4 7.8 2.3Red 0.0 157.8 2.0 1.4 9.0 48.5 100.0 73.1 29.5 9.0 Yellow- 0.0 1.0 4.256.6 100.0 123.4 144.9 88.8 34.4 10.5 Green Cyan 0.1 0.5 53.0 100.0 65.041.6 23.1 11.6 4.2 0.6

Example 3

A semiconductor light emitting device was simulated having four LEDstrings. A first LED string is driven by a blue LED having peak emissionwavelength of approximately 450 nm to approximately 455 nm, utilizes arecipient luminophoric medium, and generates a combined emission of ablue color point with a 1931 CIE chromaticity diagram color point of(0.2219, 0.1755). A second LED string is driven by a blue LED havingpeak emission wavelength of approximately 450 nm to approximately 455nm, utilizes a recipient luminophoric medium, and generates a combinedemission of a red color point with a 1931 CIE chromaticity diagram colorpoint of (0.5702, 0.3869). A third LED string is driven by a blue LEDhaving peak emission wavelength of approximately 450 nm to approximately455 nm, utilizes a recipient luminophoric medium, and generates acombined emission of a yellow/green color point with a 1931 CIEchromaticity diagram color point of (0.3722, 0.4232). A fourth LEDstring is driven by a cyan LED having a peak emission wavelength ofapproximately 505 nm, utilizes a recipient luminophoric medium, andgenerates a combined emission of a cyan color point with a 1931 CIEchromaticity diagram color point of (0.3704, 0.5083). FIGS. 11A-11Cshows color-rendering characteristics of the device for a representativeselection of white light color points near the Planckian locus, withdata shown for white light generated in different operational modesusing combinations of the first, second, third, and fourth LED strings.FIG. 11D shows comparisons of circadian action factor values for whitelight points generated at similar CCT values under different operationalmodes. Table 4 below shows the spectral power distributions for theblue, red, yellow-green, and cyan color points generated by the deviceof this Example, with spectral power shown within wavelength ranges innanometers from 380 nm to 780 nm, with an arbitrary reference wavelengthrange selected for each color range and normalized to a value of 100.0:

TABLE 4 380-420 421-460 461-500 501-540 541-580 581-620 621-660 661-700701-740 741-780 Blue 8.1 100.0 188.1 35.6 40.0 70.0 80.2 12.4 2.3 1.0Red 0.7 2.1 4.1 12.2 20.5 51.8 100.0 74.3 29.3 8.4 Yellow- 1.0 25.3 52.777.5 100.0 80.5 62.0 35.1 13.3 4.0 Green Cyan 0.4 1.5 55.5 100.0 65.359.9 57.1 35.0 13.5 4.1

Example 4

A semiconductor light emitting device was simulated having four LEDstrings. A first LED string is driven by a blue LED having peak emissionwavelength of approximately 450 nm to approximately 455 nm, utilizes arecipient luminophoric medium, and generates a combined emission of ablue color point with a 1931 CIE chromaticity diagram color point of(0.2387, 0.1692). A second LED string is driven by a blue LED havingpeak emission wavelength of approximately 450 nm to approximately 455nm, utilizes a recipient luminophoric medium, and generates a combinedemission of a red color point with a 1931 CIE chromaticity diagram colorpoint of (0.5563, 0.3072). A third LED string is driven by a blue LEDhaving peak emission wavelength of approximately 450 nm to approximately455 nm, utilizes a recipient luminophoric medium, and generates acombined emission of a yellow/green color point with a 1931 CIEchromaticity diagram color point of (0.4494, 0.5161). A fourth LEDstring is driven by a cyan LED having a peak emission wavelength ofapproximately 505 nm, utilizes a recipient luminophoric medium, andgenerates a combined emission of a cyan color point with a 1931 CIEchromaticity diagram color point of (0.3548, 0.5484). FIGS. 12A-12Cshows color-rendering characteristics of the device for a representativeselection of white light color points near the Planckian locus, withdata shown for white light generated in different operational modesusing combinations of the first, second, third, and fourth LED strings.FIG. 12D shows comparisons of circadian action factor values for whitelight points generated at similar CCT values under different operationalmodes. Table 5 below shows the spectral power distributions for theblue, red, yellow-green, and cyan color points generated by the deviceof this Example, with spectral power shown within wavelength ranges innanometers from 380 nm to 780 nm, with an arbitrary reference wavelengthrange selected for each color range and normalized to a value of 100.0:

TABLE 5 380-420 421-460 461-500 501-540 541-580 581-620 621-660 661-700701-740 741-780 Blue 1.9 100.0 34.4 32.1 40.5 29.0 15.4 5.9 2.8 1.5 Red14.8 10.5 6.7 8.7 8.7 102.8 100.0 11.0 1.5 1.1 Yellow- 1.1 2.3 5.9 61.0100.0 85.0 51.0 12.6 3.2 1.0 Green Cyan 0.7 1.6 39.6 100.0 80.4 53.024.9 9.5 3.3 1.2

Example 5

A semiconductor light emitting device was simulated having four LEDstrings. A first LED string is driven by a blue LED having peak emissionwavelength of approximately 450 nm to approximately 455 nm, utilizes arecipient luminophoric medium, and generates a combined emission of ablue color point with a 1931 CIE chromaticity diagram color point of(0.2524, 0.223). A second LED string is driven by a blue LED having peakemission wavelength of approximately 450 nm to approximately 455 nm,utilizes a recipient luminophoric medium, and generates a combinedemission of a red color point with a 1931 CIE chromaticity diagram colorpoint of (0.5941, 0.3215). A third LED string is driven by a blue LEDhaving peak emission wavelength of approximately 450 nm to approximately455 nm, utilizes a recipient luminophoric medium, and generates acombined emission of a yellow/green color point with a 1931 CIEchromaticity diagram color point of (0.4338, 0.5195). A fourth LEDstring is driven by a cyan LED having a peak emission wavelength ofapproximately 505 nm, utilizes a recipient luminophoric medium, andgenerates a combined emission of a cyan color point with a 1931 CIEchromaticity diagram color point of (0.3361, 0.5257). FIGS. 13A-13Cshows color-rendering characteristics of the device for a representativeselection of white light color points near the Planckian locus, withdata shown for white light generated in different operational modesusing combinations of the first, second, third, and fourth LED strings.FIG. 13D shows comparisons of circadian action factor values for whitelight points generated at similar CCT values under different operationalmodes. Table 6 below shows the spectral power distributions for theblue, red, yellow-green, and cyan color points generated by the deviceof this Example, with spectral power shown within wavelength ranges innanometers from 380 nm to 780 nm, with an arbitrary reference wavelengthrange selected for each color range and normalized to a value of 100.0:

TABLE 6 380-420 421-460 461-500 501-540 541-580 581-620 621-660 661-700701-740 741-780 Blue 1.9 100.0 34.4 32.1 40.5 29.0 15.4 5.9 2.8 1.5 Red0.2 8.5 3.0 5.5 9.5 60.7 100.0 1.8 0.5 0.3 Yellow- 0.8 5.6 6.3 73.4100.0 83.8 48.4 19.5 6.5 2.0 Green Cyan 0.2 1.4 58.6 100.0 62.0 47.528.2 6.6 1.8 0.6

Those of ordinary skill in the art will appreciate that a variety ofmaterials can be used in the manufacturing of the components in thedevices and systems disclosed herein. Any suitable structure and/ormaterial can be used for the various features described herein, and askilled artisan will be able to select an appropriate structures andmaterials based on various considerations, including the intended use ofthe systems disclosed herein, the intended arena within which they willbe used, and the equipment and/or accessories with which they areintended to be used, among other considerations. Conventional polymeric,metal-polymer composites, ceramics, and metal materials are suitable foruse in the various components. Materials hereinafter discovered and/ordeveloped that are determined to be suitable for use in the features andelements described herein would also be considered acceptable.

When ranges are used herein for physical properties, such as molecularweight, or chemical properties, such as chemical formulae, allcombinations, and subcombinations of ranges for specific exemplartherein are intended to be included.

The disclosures of each patent, patent application, and publicationcited or described in this document are hereby incorporated herein byreference, in its entirety.

Those of ordinary skill in the art will appreciate that numerous changesand modifications can be made to the exemplars of the disclosure andthat such changes and modifications can be made without departing fromthe spirit of the disclosure. It is, therefore, intended that theappended claims cover all such equivalent variations as fall within thetrue spirit and scope of the disclosure.

What is claimed:
 1. A method of generating white light, the methodcomprising: producing light from a first light emitting diode (“LED”)string; producing light from a second LED string; producing light from athird LED string, a fourth LED string, or both the third LED string andthe fourth LED string; and passing the light produced by each of thefirst, second, third, and fourth LED strings through one of a pluralityof respective luminophoric mediums; combining the light exiting theplurality of respective luminophoric mediums together into white light;wherein the combined white light corresponds to at least one of aplurality of points along a predefined path near the black body locus inthe 1931 CIE Chromaticity Diagram; wherein one or more of the first,second, third, and fourth LED strings comprises a ultraviolet or violetLED having a peak wavelength of between about 360 nm and about 430 nm.2. The method of claim 1, wherein: the light produced from the first LEDstring is passed through a first recipient luminophoric medium thatcomprises a first luminescent material, wherein light exiting the firstluminophoric medium comprises unsaturated light having a first colorpoint within a blue color range; the light produced from the second LEDstring is passed through a second recipient luminophoric medium thatcomprises a second luminescent material, wherein the light exiting thesecond luminophoric medium comprises unsaturated light having a secondcolor point within a red color range; the light produced from the thirdLED string is passed through a third recipient luminophoric medium thatcomprises a third luminescent material, wherein the light exiting thethird luminophoric medium comprises unsaturated light having a thirdcolor point within a yellow/green color range; and the light producedfrom the fourth LED string is passed through a fourth recipientluminophoric medium that comprises a fourth luminescent material,wherein the light exiting the fourth luminophoric medium comprisesunsaturated light having a fourth color point within a cyan color range.3. The method of claim 2, wherein the blue color range is defined by aline connecting the ccx, ccy color coordinates of the infinity point ofthe Planckian locus (0.242, 0.24) and (0.12, 0.068), the Planckian locusfrom 4000K and infinite CCT, the constant CCT line of 4000K, the line ofpurples, and the spectral locus the red color range is defined by thespectral locus between the constant CCT line of 1600K and the line ofpurples, the line of purples, a line connecting the ccx, ccy colorcoordinates (0.61, 0.21) and (0.47, 0.28), and the constant CCT line of1600K the yellow/green color range is defined by the constant CCT lineof 4600K, the Planckian locus between 4600K and 550K, the spectrallocus, and a line connecting the ccx, ccy color coordinates (0.445,0.555) and (0.38, 0.505); the cyan color range is defined by a lineconnecting the ccx, ccy color coordinates (0.18, 0.55) and (0.27, 0.72),the constant CCT line of 9000K, the Planckian locus between 9000K and4600K, the constant CCT line of 4600K, and the spectral locus.
 4. Themethod of claim 2, wherein the blue color range comprises a region onthe 1931 CIE Chromaticity Diagram defined by a 60-step MacAdam ellipseat 20000K, 40 points below the Planckian locus.
 5. The method of claim2, wherein the red color range comprises a region on the 1931 CIEChromaticity Diagram defined by a 20-step MacAdam ellipse at 1200K, 20points below the Planckian locus.
 6. The method of claim 2, wherein theyellow/green color range comprises a region on the 1931 CIE ChromaticityDiagram defined by a 16-step MacAdam ellipse at 3700K, 30 points abovePlanckian locus.
 7. The method of claim 2, wherein the cyan color rangecomprises a region on the 1931 CIE Chromaticity Diagram defined by30-step MacAdam ellipse at 6000K, 68 points above the Planckian locus.8. The method of claim 2, wherein the generated white light falls withina 7-step MacAdam ellipse around any point on the black body locus havinga correlated color temperature between 1800K and 4200K; and wherein thegenerated white light corresponds to a plurality of points along apredefined path with the light generated at each point having light withRa≥80, R9≥50, or both.
 9. The method of claim 8, wherein the methodfurther comprises generating white light within a 7-step MacAdam ellipseof a plurality of target CCTs selected from between 1800K and 4200K viaa plurality of emitting modes, the emitting modes comprising: a firstemitting mode, wherein the method comprises producing light from thefirst, second, third, and fourth LED strings; a second emitting mode,wherein the method comprises producing light from the first, second, andthird LED strings but not the fourth LED string; and a third emittingmode, wherein the method comprises producing light from the first,second, and fourth LED strings but not the third LED string.
 10. Themethod of claim 9, wherein for each target CCT, the respective circadianaction factor values of the white light generated in any two of thefirst, second, and third emitting modes differ from each other by apredetermined threshold amount.
 11. The method of claim 10, wherein thepredetermined threshold amount is about 100%.
 12. The method of claim10, wherein the predetermined threshold amount is about 75%.
 13. Themethod of claim 10, wherein the predetermined threshold amount is about50%.
 14. The method of claim 10, wherein the predetermined thresholdamount is about 30%.
 15. The method of any of claims 1-14, wherein thefirst, second, and third LED strings comprise a ultraviolet or violetLED having a peak wavelength of between about 360 nm and about 430 nmand the fourth LED string comprises a cyan LED having a peak wavelengthof between about 485 nm and about 520 nm.
 16. The method of claim 9,wherein for each target CCT, the white light generated in two of thelight emitting modes is within about 1.0 standard deviations of colormatching (SDCM).
 17. The method of claim 9, wherein for each target CCT,the white light generated in two of the light emitting modes is withinabout 0.5 standard deviations of color matching (SDCM).